Litter boxes for domestic pets, more especially for cats, are well known. The most common and oldest prior art is the traditional "sandbox". A box, of any material, is filled with sand and placed in the household. To dispose of soiled litter and fecal matter the sandbox the sandbox is emptied manually. Perforated or slotted scoops have since been developed as a means to remove soiled litter and fecal matter. As well, the introduction of "clumping" litter that, when soiled, clumps together has increased the effectiveness of the perforated or slotted scoop for removing soiled litter. However, given that while the majority of the soiled litter and fecal matter may be removed by means previously described, the entire contents of the sandbox or litter box must be emptied and disposed of from time to time. Typically, both the cleaning and changing of litter requires significant human contact with the litter. Contact with domestic pet waste, cat urine in particular, is potentially very dangerous for pregnant women and has been known to cause miscarriages. In addition, the odour associated with domestic pet waste can be particularly offensive and in some cases may cause nausea. More recently, chambers have been introduced in an attempt to overcome the aforementioned problems. Numerous configurations using a chamber, a filter, and disposable means, allow for a more contained litter box which may be rotatable. The filter essentially replaces the perforated or slotted scoop and is mounted on the inner wall of the chamber and acts to separate the waste material from the clean litter. Limitations of the prior art encompass filter difficulty in terms of retaining waste material on the filter and the absence of a simple means for the addition of clean litter.
A self-cleaning litter box in keeping with the present invention avoids the previously described limitations of the prior art. A self-cleaning litter box such as this comprises a rotatable drum, a spiral filter, a stationary back plate, drive means, and switch means. The cylindrical drum has both front and back walls, an axis of rotation, and support means. The spiral filter is mounted on the inner surface of the drum and at least 10.degree. from the bottommost point of the drum when at its rest position. The filter effectively scoops clumped soiled litter and fecal matter from the bottommost region of the rotating drum and collects the waste material on the filter. There is a first opening in the back wall of the drum and second and third openings in the back plate. When the first and second openings are aligned, it allows passage of clumped soiled litter and fecal matter collected by the filter into disposable means through the aligned openings. When the first and third openings are aligned, clean litter from a reservoir may be dispensed into the drum through the aligned openings.